This invention relates generally to the radio transmission and reception arts and more particularly to a novel and improved transceiver. While the invention may find utility in a broad variety of applications, the disclosure thereof will be facilitated by referring particularly to a portable, VHF transceiver.
Various bands or ranges of radio frequencies have been assigned by the U.S. Federal Communications Commission ("FCC") to be used for specific purposes and/or by specific users. For example, the frequencies between 88.1 and 107.9 MHz are divided into 200 KHz wide channels for use in commerical FM broadcasting. Similarly, the frequencies from 108 MHz to 136 MHz are divided into 25 KHz channels for use in civil aviation. The VHF bands include frequencies in the range of 136 MHz to 174 MHz and are divided into channels of varying widths for various uses.
It is this latter range of frequencies, 136 MHz through 174 MHz, to which the present disclosure is directed. However, it will be understood that the principles of the invention are applicable to other ranges of frequencies as well.
Moreover, within given frequency ranges, there are numerous radio-frequency divisions and sub-divisions which are mandated by the FCC, by both the purpose of the use and the identity of the user. These divisions may be several megahertz wide and the sub-divisions may be 5 KHz or 25 KHz wide. For example, generally speaking, the frequencies in the range from 138 MHz to 144 MHz are reserved for use by agencies or units of government, whether federal, state or local. In the same fashion, the frequencies from 144 MHz through 148 MHz are reserved for use by amateur or "ham" radio operators. Finally, the so-called VHF-high band, which includes carrier-frequencies from 148 MHz to 174 MHz, is sub-divided for a plurality of uses including commercial use by businesses.
Heretofore, it has been customary to provide a transceiver unit specially designed for two-way communications on one or more channels in a relatively small segment or portion of the foregoing frequency ranges or bands. For example, one wishing to operate on channels in the amateur-frequency ranges would purchase a transceiver capable of transmission and reception only in the 144 MHz to 148 MHz range. Substantial modification to such a transceiver would be necessary to enable transmission or reception on other channels or in other ranges. Moreover, such modifications may be prohibited by the FCC, which generally requires pre-approval of a transceiver unit as built and supplied by the manufacturer, and does not permit modifications of such units to broadcast in frequency ranges other than the "pre-approved" ones.
Accordingly, an individual or business desirous of two-way communication on channels located in more than one of the FCC-mandated and assigned channels has heretofore often been obliged to purchase separate transceiver equipment for each channel.
Advantageously, the present invention provides a novel transceiver which is capable of economically providing two-way communications at any carrier frequency in the 136 MHz to 174 MHz range of frequencies. Moreover, the transceiver in accordance with the invention is capable of being customized for a particular user's requirements for transmission and reception over a plurality of channels at widely-spaced frequencies within the foregoing relatively wide frequency ranges. As will be seen, the preferred embodiment of the transceiver of the invention described herein readily may be factory "programmed" to transmit and receive on a plurality of selected channels having carrier frequencies at any point within two separate and selectable 3-MHz wide segments of the foregoing range of frequencies. More or fewer such segments, as well as wider or narrower segments, or course may be provided without departing from the principles of the present invention.
For example, an individual or business which wishes two-way communications in a "business use" band (e.g., 150.815 to 150.995 MHz and 151.625 to 151.955 MHz) and in the marine band (i.e, 161.600 to 162.000 MHz) need only so specify when ordering a transceiver unit constructed in accordance with the invention. The transceiver of the invention may then be customized, quickly, easily and economically, for operation at a plurality of selected channels in these two bands. Advantageously, this provides a two-way communication system between salesmen or workers in the field, for example, and their offices or dispatchers, as the case may be, over selected channels at frequencies approved by the FCC for such use, but in relatively widely-shaped frequency ranges, without any interference either to or from transmissions taking place in closely adjacent channel frequencies.
Achieving the foregoing operations by conventional devices required a relatively bulky, complex and expensive transceiver. The present invention, however, advantageously achieves such operations in a relatively small and inexpensive, portable, battery-powered unit. Moreover, the invention advantageously utilizes relatively inexpensive and yet highly-reliable, microprocessor-controlled frequency-synthesized circuitry to achieve this operation.
More specifically, the provision of sufficient central processing unit ("CPU") or microprocessor ("processor") and related memory capacity to synthesize local-oscillator frequencies for various channels in the broad frequency ranges mentioned above has heretofore been relatively complex and costly. However, the transceiver of the present invention advantageously provides such features with but a minimum of processor capacity and memory space, hence requiring only relatively inexpensive and commercially-available processor components.
As an additional advantage, the transceiver of the illustrated embodiment utilizes frequency-synthesized, phase-locked loop ("PLL") tuning under the control of the novel CPU circuitry so as to achieve surprising accuracy in the tuning of each channel or carrier frequency selected within each of the pre-selected segments. Additional advantageous features of the present invention will become apparent upon reading the detailed description of the illustrated embodiment hereinbelow.